Public opinion and use of US military might

There is a perceptible dovishness among Pentagon hawks these days. Not that these labels were ever very accurate. But from the upper reaches of the Pentagon, senior military officers are warning President Reagan and the nation not to get heavily involved militarily in world trouble spots. From the Joint Chiefs of Staff on down, uniformed leaders are saying United States troops should not be sent to places like Central America, and that countries like El Salvador will have to win their peace largely through their own efforts.

Defense Secretary Caspar W. Weinberger, following the counsel of his senior uniformed advisers, was among those cautioning against a large presence and lengthy US stay in Lebanon.

''It's amazing how many ways these guys can find to avoid going to war,'' notes a senior US intelligence official, with some irony.

At the root of this seeming role reversal is one of the lessons of Vietnam: that commitment of military forces cannot be successful without solid public support, and that the nation and its leaderhip must know why they're using American power and what the goals for success are.

The principal proponent of this view today is a teacher and prolific writer at the Army War College at Carlisle Barracks.

Col. Harry G. Summers Jr., who is gaining widespread public recognition for his analysis and historical perspective, is a highly decorated infantry veteran of Korea and Vietnam (Silver Star, several Purple Hearts), a former top aide to senior military leadership, and a US negotiator in Hanoi. Yet he is also an avuncular and rotund professorial type who does not fit the spit-and-polish mold.

His new book, ''On Strategy,'' a critical assessment of the Vietnam war, concludes that US political and military leaders failed in Southeast Asia because they either didn't understand or ignored basic principles of warfare. Even though he doesn't spare the military in his criticisms, his writings and course on military history and its application to the prese t and future are being hailed at the highest levels of the civilian and military defense establishment.

Although there was some resistance within the Army to reliving Vietnam, however instructive it might be, Army Chief of Staff Edward C. Meyer and the Joint Chiefs chairman, Gen. John W. Vessey Jr., are among the book's strongest supporters. Every member of Congress has received the book, and Secretary Weinberger ordered 20 extra copies.

In an interview, Colonel Summers explained why there are ''fundamental limitations on the use of military power,'' why ''the direct application of US military power may very well be counterproductive,'' and how this applies to places like Central America.

For the students here at Carlisle Barracks (mostly lieutenant colonels who are now at about the 20-year point in their careers), he does this by using history to illuminate theory. The most relevant history for this cream of the Army's Vietnam crop (they were young lieutenants and captains there) is their own experience in Southeast Asia. While citing the broad scope and depth of military history, Summers uses as his principal text the 18th-century classic ''On War'' by Carl von Clausewitz.

He concludes that the US, including its military leadership, failed to follow Clausewitz's teachings, most notably the absolute necessity for rallying public support before committing troops to battle.

''Tactical victory may very well be at the price of strategic defeat in losing the support of the people at home,'' Summers said. Today, he added, ''the military are warning the political leadership of the criticality of this public support for any military operation.

''If the American people don't want us to go someplace,'' he said, ''we ought not to go.''

Besides the current lack of support among Americans for substantial US military intervention in Central America, there is also the question of whether such involvement would help bring stability and peace to the region.

Summers thinks not: ''One of the lessons of Vietnam is that there are fundamental and inherent limitations on what an outside power can do in support of an ally faced with an insurgency. We can help them with training, we can help them with political and economic assistance. But when you inject foreign troops into the area, you exacerbate the problem more than you cure it.

''If El Salvador was faced with a cross-border invasion by the regular forces of Nicaragua or Cuba, then perhaps there's a legitimate role for US military forces to deal with this external aggression. But for internal security, it has to be the government involved.''

Institutionally, it's important that such lessons be clearly understood by the Army and other military services, Summers says. Senior military commanders from the Vietnam era have retired, and most officers who have recently decided to make the military a career (majors and lieutenant commanders) are too young to have fought in Vietnam.

''It's a fast-moving train and we're quickly losing our Vietnam experience,'' he says. ''It's important for the Army to understand what went wrong in Vietnam so that we avoid those kinds of pitfalls in the future.''

With the superpowers having reached a nuclear standoff of sorts, there is also renewed emphasis in the American armed forces (as well as in the NATO alliance) on the role and importance of conventional forces. The lessons of Vietnam apply here as well.

Then, too, Summers has a personal reason for seeing that the mistakes of the past are not repeated. His two sons are young captains in the United States Army.